The present invention relates to a snap-lock packing element, a contact assembly made from snap-lock packing elements and methods of assembly of the snap-lock packing elements to make the contact assembly. More particularly, the invention relates to a snap-lock packing element that can be readily and easily assembled together using little force with like packing elements by connecting the packing elements with connectors in a snap-lock manner such that the packing elements cannot be separated without such force that the material forming at least one of components of the snap-lock connections or the packing element will fail to the extent that a contact assembly made using the packing elements would not be functional.
Packing elements are often used as contact assemblies or bodies in heat exchange apparatus such as cooling towers where gas, such as air is in contact with liquid, such as water, to provide heat exchange in systems where the gas and liquid typically flow countercurrent or crosscurrent to one another. Contact assemblies are also used in other industries where a contact between gases, liquids and even particulate solids are involved, such as gas scrubbers, as well as in water treatment facilities, such as in trickling filters, for example, where the contact assemblies support bacteria used in water treatment systems. Since the most common use for the packing elements of the present invention is likely to make contact assemblies for heat exchangers, the invention will primarily be described with such use in mind, although the packing elements and contact assemblies made from them are not to be limited only for heat exchange applications.
In the heat exchange industry, for example, such packing elements and contact assemblies or bodies made from them, are often referred to a “fill,” “media” or “fill media.” One type of fill media that has been sold by Brentwood Industries, Inc. the applicant of this patent application, is HTP-25™ splash fill media in its ACCU-PAC® fill media line, used in high temperature counterflow or cross-flow cooling towers. This is an injection-molded polypropylene copolymer fill media that produces heat transfer by way of integral splash or drip points in a compact module, assembly or body made of connected, corrugated lattice packing elements. The highly engineered splash design formed using the lattice packing elements provides maximum thermal performance. The open lattice, offset flute, corrugated packing elements are fouling-resistant that is excellent for use in environments and systems where the circulating water has very high levels of suspended solids.
The HTP-25™ fill media is commercially successful and provides many advantages in cooling tower environments, partially attributable to the strength of the contact assembly or body formed from the packing elements using a very secure mechanical assembly or fastening technique, rather than using solvents or adhesives that are a less environmentally friendly way of securing together the packing elements to make the contact assemblies. The mechanical fastening technique used for this type of fill media involves inserting relatively long cylindrical projections extending from one packing element through mating holes in an adjacent packing element. Once a projection has been inserted through a hole, the projection is then mechanically deformed using various types of crimping tools to form an expanded head on the projection, such that the deformed projection acts as a flattened rivet with a top plan size larger than the hole diameter, by which the expanded head cannot be retracted through the hole, retaining the packing elements together. This produces a very strong contact body or contact assembly.
The present invention is an improvement over the current HTP-25™ splash fill media, where the same materials and general lattice packing elements or contact sheets can be used, but with the snap-lock connectors of the present invention the packing elements are able to be formed very easily and readily in the field by hand without apparatus including crimping tools previously required to form the projections into flattened rivets. With the present invention, either no apparatus is needed or a simple fixture having a base plate and a plurality of alignment rods can be used where the alignment rods pass through alignment holes in adjacent packing elements. The resulting contact assembly made by connecting the packing elements is still so strong that the connecting members of the snap-lock connections would be rendered dysfunctional or useless, or the material of the packing elements would, in essence, be destroyed, if the packing elements were attempted to be separated from each other after the snap-lock connections are formed.
When not assembled to form a contact assembly or contact body, the packing elements of the HTP-25™ splash fill media can nest together for storage and shipment, but the nesting height is relatively high because of the height of the projections that are required to be flattened to form the couplings into flattened rivets. In the current embodiment of the HTP-25™ splash fill media, the packing elements can stack and nest together for storage and shipment, but the nesting height from the bottom of one lower packing element to the bottom of the next adjacent upper packing element is 0.227 inch (5.766 mm). This corresponds with a nesting height of about 48 packing elements per foot (30.38 cm). Since storage of the packing elements requires an adequate amount of volume, and shipping also may be based at least in part on volume, it is desired to have a lower nesting height for packing elements of otherwise identical dimensions. The packing element of the present invention, which are connectable together into a contact assembly in a snap-lock manner, has a significantly lower unassembled stacking or nesting height compared to packing elements of the same dimensions, other than the type of connector, currently used for the HTP-25™ splash fill media. This provides a considerable saving of storage space and shipping costs for the packing elements of the present invention.
Another advantage of the present invention is that the injection molding tool used to form the packing elements does not require moving parts. The snap-lock connection of the present invention includes a post member having a cap with legs and undercut bottom edges, as explained below. These undercut bottom edges are designed to be formed by fixed mold protrusions that extend from the opposite side of an injection mold to the undercut areas so that the injection molding operation can be performed more easily, including merely opening the mold to release the packing element including the post member with complex undercut geometries. Mold cavity parts moving in the plane of the tool face are typically used to create complex geometries with undercut areas in general, where traditional cantilever undercut connections are present. Such moving parts are not necessary to mold the undercut bottom edges of the post member cap in the present invention. Therefore, the cost of the tool is reduced over a tool having moving or mechanical features that operate in a plane parallel to the tool face.